1. Field of the Invention
The present invention relates to radiographic industrial inspection such as the radiographic inspection of pipe; and more particularly the invention relates to the radiographic inspection of pipe as in erosion/corrosion control, wherein the pipe or pipe joint is radiographically reproduced on film and the wall erosion is measured against a constant factor.
2. General Background
In the chemical, refinery, oil and gas and other such industries, which utilize pipe for the conveying of a variety of liquid and gaseous materials as well as solid materials in slurry form, during the transport of these materials in the pipe, pipes are frequently subjected to mechanical erosion and corrosion within, based upon the materials which they convey.
In the art of corrosion and erosion control it is often desirable to inspect these installed pipes on a periodic basis in order to determine whether or not wear has occurred which would jeopardize a safe operation. The erosion would normally occur in critical points of the pipe, such as elbow joints or "T" joints, wherever fluid contact being transported is most severe and thus would cause erosion of the pipes inner wall. Extensive wear on piping can produce dangerously thin pipe wall thickness which could result in a fracture or rupture of the pipe and resulting in some cases a catastrophy, such as a fire or explosion.
The radiographic art has developed a system for inspecting pipe which normally involves the use of radiation which is transmitted at the pipe to be inspected with a film pack having X-ray film therewithin being placed under the pipe opposite the ray producing camera so that a representation of the pipe is produced onto the X-ray film.
The use of radiography for inspecting pipe as well as numerous pipe fittings attached to the pipe is often done using typically a cassette which contains a sheet of X-ray film and usually two screens placed on each side of the film. The result of this type of X-ray procedure produces a representation on the X-ray film which must be placed against an illuminated background of light in order to be read and interpreted.
In the present state of the art, using known systems, technicians attempt to interpret the thickness of the pipe from the representation of the X-ray with the use of calipers or other measuring tools and in many instances using a known control element in the same exposure, such as a magnet, for example, attached to the side of the pipe. The magnet, or perhaps other objects such as a shim or metal block of known thickness is then measured in comparison to the distance from the X-ray source from which the pipe was X-rayed. This system falls short, in view of the fact that often the edges of the magnet or shim used become blurred, and it becomes increasingly difficult to measure with exactness to the comparison factor. Also, if the distance from the pipe has been inaccurately determined, an error in the comparison reading would occur.